SD Card Resistors, required for SPI ?

Jack Scarlet

Hello, are resistors required between an SD card and a Propeller ? I vaguely remember someone once saying they didn't use them and all was well.

pik33

I don't use any resistors to connect SD card, only a small electrolitic capacitor between vcc and vdd. It worked with 3 or 4 different micro sd cards (2..8 GB)

whicker

If you are going to insert and remove the SD card with the system power on, and want reliability, then yes the resistors would be a good idea.

Otherwise, if you're just experimenting for fun, and you know to just power off and on again if it gets stuck, then no, don't worry about it.

Toby Seckshund

I have always put the 4 resistors (10K) for the SPI lines (I have seen other sites saying that it would be good to pull up the others too).

A 10uF and a 100nF very close to the card and the shortest wiring possible seems to give more reliable results (but I do have a "DracBlade" clone, in a KBD, with the wires quite long and the caps back on the PCB)

Peter Jakacki

If there's one signal I don't put a pullup on then it's the card select line because the SD card itself has a pullup on this line and you can use this to detect for a card rather than the more complicated arrangement via the CD switch. Having a pullup on the MISO line (data from the card) is helpful but not required either. SD guidelines recommend pullups on unused lines though. So it's possible to run the card without ay pullups at all, especially the card select line.

Jack Scarlet

Excellent! Thanks for all the replies, great info!